/*
 * Copyright (C) 2020 The Android Open Source Project
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package com.android.server.utils;

import android.annotation.Nullable;

/**
 * This class receives notifications when watched objects detect changes.
 * Must be implemented by objects which are registered to a {@link Watchable}.
 */
public abstract class Watcher {

    /**
     * This method is called when {@link Watchable} detects a change.  The <what>
     * parameter indicates what changed, but it may be null.  The parameter is intended
     * for debugging.
     *
     * @param what The {@link Watchable} that changed.
     */
    public abstract void onChange(@Nullable Watchable what);
}
